In recent years, various kinds of software data (hereinafter referred to as “content”), such as audio data such as music, image data such as movies, game programs, and various kinds of application programs have been distributed via a network such as the Internet or through recording media such as DVDs and CDs. This distributed content is used by being played back in a PC (Personal Computer), a CD player, a DVD player, etc., owned by a user.
Regarding most content, such as music data, image data, etc., in general, the distribution right is owned by the creator thereof or a seller thereof. Therefore, in order to play back or use normal content other than an exceptional free-of-charge distributed content, it is necessary to obtain an authorized content usage right. For example, in the case of a CD, a purchase of a CD by paying a price appropriate for the CD is a condition for playback in a player.
Furthermore, when content is to be received via a network such as the Internet by using a PC, a communication terminal, etc., content is provided from a provider under the condition that the user pays a price appropriate for content usage to the content provider by inputting user information such as the user's credit number.
However, even if such a price payment process during content provision is performed, illegally copied data will spread if a user who obtains content performs recording from, for example, a CD into another recording medium (so-called copying), or if a so-called ripping process in which, in a PC, etc., content is read as digital data from a CD, etc., and is stored as a file in the computer is permitted.
Ripping in a PC, etc., is a process of copying data digitally, and the quality of the original data is maintained. When the ripped data is written into another CD-R, a content CD having exactly the same quality as that of the original CD is created. Furthermore, it also becomes possible to record ripped data as compressed MP3 data, etc., or to transmit the ripped data via a network.
As described above, the situation in which copyrighted content is illegally copied or altered after the content is temporarily passed to a user and then distributed is undesirable from the viewpoint of copyright protection.
As copyright protection technology for preventing such a situation, an information recording medium provided with a copy control function (for example, a CD with a copy prevention function) has been developed. Examples of the copy prevention functions include copy control technology developed by Midbar Technologies Ltd., and copy control technology developed by US Macrovision Corporation.
The above have a configuration in which, for example, as a result of recording a pseudo-signal in a first track of a CD, when the CD is set in a CD-ROM drive of a PC, the PC does not recognize it as a music CD, making it impossible to perform a playback process using a CD player program of the PC. An ordinary CD player, which is incapable of performing a ripping process, can perform playback of only content data by ignoring the pseudo-signal.
In the manner described above, if attempts are made to play back an information recording medium such as a CD in which copy-controlled content is recorded, as described above, playback is possible in a playback-only CD player, but playback is impossible in a PC, etc. Although this offers the advantages that illegal processes such as copying or ripping are eliminated, it is inconvenient for an authorized content usage user who does not have the intention of performing illegal copying or ripping.